1. Field of the Invention
The present invention relates to an apparatus for controlling a vehicle such as a motorized skateboard and also relates to a vehicle equipped with such a control unit. More particularly, the present invention relates to driving control of such a vehicle while the user is stepping on/off the vehicle or riding the vehicle.
2. Description of the Related Art
Motorized skateboards, motorized surfboards, motorized wheelchairs and other vehicles have been known as motorized vehicles that are driven by an electric motor. The user of such a motorized vehicle can control the velocity of (i.e., accelerate or decelerate) the vehicle or change the direction of travel from forward to backward, or vice versa, by manually operating a throttle lever, a joystick or any other control lever.
However, while driving such a motorized vehicle that requires manual operation, the user is apt to pay too much attention to the operation to drive it comfortably. Also, if such a manual operation member is provided, the user can change his or her riding position less freely.
Japanese Patent Application Laid-Open Publication No. 10-23613 discloses a motorized vehicle that does not require the user to perform such a manual operation. In the motorized vehicle disclosed in the Japanese Patent Application Laid-Open Publication No. 10-23613, two pressure sensors, located at front and rear positions of a skateboard, each sense the given load (i.e., the weight of the user). Then, based on the difference between the load values detected by these sensors, a motor is controlled and wheels are driven, thereby propelling the skateboard either forward or backward.
More particularly, this skateboard travels forward if the load placed on the front pressure sensor is heavier than that placed on the rear pressure sensor but travels backward if the load placed on the front pressure sensor is lighter than that placed on the rear pressure sensor. Also, this skateboard accelerates as the difference between the loads placed on the front and rear pressure sensors widens but decelerates as the difference narrows.
Generally speaking, however, it is not easy for every user to control such a motorized skateboard just as he or she intends because he or she has to learn some skills to start or stop the skateboard without stumbling. That is to say, it usually takes a lot of time to master those skills of operation and to use such a motorized vehicle safely. This is because a conventional motorized skateboard that requires no manual operation often works against the will and intended action of the user while he or she is stepping on or off the board.
For example, suppose the velocity of the motorized skateboard is controlled according to the difference between the loads placed on the front and rear pressure sensors. In that case, if the difference between the loads placed on the front and rear pressure sensors becomes equal to zero while the user is riding the skateboard (i.e., when the center of gravity of the user is located substantially at the center of the board), no driving force is generated anymore. That is why the user always has to lean forward while traveling forward and lean backward while traveling backward. As a result, the user gets tired more easily than usual.
Also, if the user of a motorized skateboard moves his or her rear foot off the skateboard in order to stop the skateboard while riding it with both feet placed on the board, the skateboard will accelerate against the will and intended action of the user. This is because in that situation, only the load that has been placed on the rear pressure sensor is removed and the difference between the loads placed on the front and rear pressure sensors increases. That is why it is difficult for the user to stop the skateboard by moving his or her rear foot off the board.
On the other hand, if the user puts one of his or her feet on the front portion of the motorized skateboard while the skateboard is stopped or at rest, the skateboard will start abruptly. This is because only the load placed on the front pressure sensor increases and the difference between the loads placed on the front and rear pressure sensors increases.